Method of manufacturing solid-state electrolytic capacitor

ABSTRACT

A method of manufacturing the solid electrolytic capacitors that can be directly connected to semiconductor components and have a faster response to a high frequency as well as a larger capacitance includes: a dielectric forming stage where a valve metal sheet ( 2 ) is made porous and dielectric coating ( 7 ) is provided on the porous face ( 3 ); an element forming stage where solid electrolytic layer ( 8 ) and collector layer ( 10 ) are formed on the dielectric coating ( 7 ); and a terminal forming stage where connecting terminal ( 16 ) to an external electrode is formed. The element forming stage includes the steps of: forming solid electrolytic layer ( 8 ); forming through-hole electrode ( 9 ) in through-hole ( 5 ) that is prepared on valve metal sheet ( 2 ); and forming collector ( 10 ) on solid electrolytic layer ( 8 ).

TECHNICAL FIELD

[0001] The present invention relates to a method of manufacturing solidelectrolytic capacitors to be used in various electronic apparatuses.

BACKGROUND ART

[0002] A structure of a conventional solid electrolytic capacitor isdescribed hereinafter with reference to its manufacturing steps. (1)Form a dielectric coating on a face of a porous section of a valve metalsheet, using one face in a thickness direction or a core of anintermediate section of the porous valve metal sheet such as aluminum ortantalum as an electrode. (2) Form a collector layer on a surface of thedielectric coating. (3) Form a capacitor element by providing anelectrode layer made of metal on the collector layer. (4) Laminate thecapacitor elements. (5) Gather together the electrode sections ofrespective capacitor elements laminated or electrode layers and couplethem to an external terminal. (6) Finally, form an outer case such thatthe external terminal can be exposed.

[0003] The foregoing conventional solid electrolytic capacitor canincrease its capacitance and reduce its equivalent series resistance(hereinafter referred to as ESR), in fact, this capacitor is mounted toa circuit board via the external terminal similar to other ordinarysolid electrolytic capacitors.

[0004] The solid electrolytic capacitors, to be surface-mounted oncircuit boards like semiconductor components, are obliged to have a slowresponse to a high frequency because the presence of terminal lengths orwire lengths increases ESR and equivalent series inductance (ESL) in anactual circuit.

[0005] In order to overcome the problem discussed above, both of ananode and a cathode are placed on a surface of a solid electrolyticcapacitor so that semiconductor components can be directly mounted onthe surface, and as a result, ESR and ESL can be lowered. Such a solidelectrolytic capacitor discussed above is proposed.

DISCLOSURE OF THE INVENTION

[0006] The present invention aims to provide a method of manufacturingthe solid electrolytic capacitors that can be directly connected tosemiconductor components and have a larger capacitance as well asfaster-response to a high frequency. The manufacturing method of thepresent invention comprises the following steps:

[0007] forming through-holes at given places after forming a resist filmon a porous face of aluminum foil, one of both the foil faces havingbeen made porous by etching; then

[0008] forming insulating films on the remaining face (non-porous face,and hereinafter referred to as a flat face) and on inner walls of thethrough-holes; then

[0009] forming a dielectric coating on the porous section after removingthe resist film; and

[0010] forming a solid electrolytic layer on the dielectric coating;then

[0011] forming through-hole electrodes in the through-holes; and

[0012] forming a collector layer on the solid electrolytic layer; then

[0013] forming openings at given places of the insulating film on theflat face; and

[0014] forming connecting terminals on exposed faces of the openings andthe through-hole electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 shows a perspective view of a solid electrolytic capacitorof the present invention.

[0016]FIG. 2 shows a sectional view of a solid electrolytic capacitor ofthe present invention.

[0017]FIG. 3 shows an enlarged sectional view of an essential part of asolid electrolytic capacitor of the present invention.

[0018]FIG. 4 shows a sectional view illustrating a status where a resistfilm is formed on a porous section of an aluminum foil of a solidelectrolytic capacitor of the present invention.

[0019]FIG. 5 shows a sectional view illustrating a status wherethrough-holes are formed at given places on the aluminum foil of thesolid electrolytic capacitor of the present invention.

[0020]FIG. 6 shows a sectional view illustrating a status whereinsulating films are formed on a flat face (non-porous face) of thealuminum foil and on inner walls of the through-holes of the solidelectrolytic capacitor of the present invention.

[0021]FIG. 7 shows a sectional view illustrating a status where adielectric coating is formed on the porous section of the aluminum foilof the solid electrolytic capacitor of the present invention.

[0022]FIG. 8 shows a sectional view illustrating a status where a solidelectrolytic layer is formed on the dielectric coating on the aluminumfoil of the solid electrolytic capacitor of the present invention.

[0023]FIG. 9 shows a sectional view illustrating a status wherethrough-hole electrodes are formed in the through-holes of the solidelectrolytic capacitor of the present invention.

[0024]FIG. 10 is a sectional view illustrating a status wherethrough-hole electrodes are formed in the through-holes of the solidelectrolytic capacitor of the present invention.

[0025]FIG. 11 is a sectional view illustrating a status where openingsare formed on the insulating film of the solid electrolytic capacitor ofthe present invention.

[0026]FIG. 12 is a sectional view illustrating a status where aconnecting terminal is formed on the opening of the solid electrolyticcapacitor of the present invention.

[0027]FIG. 13 is a sectional view illustrating a status where an outercase is provided to a capacitor element of a solid electrolyticcapacitor of the present invention.

[0028]FIG. 14 is a sectional view illustrating a status where externalterminals and connecting bumps are formed on the outer case of the solidelectrolytic capacitor of the present invention.

[0029]FIG. 15 is a sectional view illustrating a status where a resistfilm is formed on an insulating film of another solid electrolyticcapacitor of the present invention.

[0030]FIG. 16 is a sectional view illustrating a status where a patternis provided to the resist film of the another solid electrolyticcapacitor of the present invention.

[0031]FIG. 17 is a sectional view illustrating a status wherethrough-hole electrodes are formed in through-holes of still anothersolid electrolytic capacitor of the present invention.

[0032]FIG. 18 is a sectional view illustrating a status where a solidelectrolytic layer is formed on a dielectric coating on an aluminum foilof the still another solid electrolytic capacitor of the presentinvention.

[0033]FIG. 19 is a sectional view illustrating a status where aninsulating film is formed on a flat face of an aluminum foil and inthrough-holes of yet another solid electrolytic capacitor of the presentinvention.

[0034]FIG. 20 is a sectional view illustrating a status where adielectric coating is formed on a porous section of an aluminum foil ofthe yet another solid electrolytic capacitor of the present invention.

[0035]FIG. 21 is a sectional view illustrating a status where a solidelectrolytic layer on the dielectric coating on the aluminum foil of theyet another solid electrolytic capacitor of the present invention.

[0036]FIG. 22 is a sectional view illustrating a status where secondthrough-holes are formed in the insulating film of the yet another solidelectrolytic capacitor of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] The manufacturing method of the present invention comprises thefollowing steps:

[0038] forming a resist film on a porous section of aluminum foil, thenforming through-holes at given places; and

[0039] forming insulating films on the remaining face (non-porous face,and hereinafter referred to as a flat face) and inner walls of thethrough-holes; then

[0040] removing the resist film; then

[0041] forming a dielectric coating on the porous section.

[0042] A set of steps hitherto discussed is referred to as a stage offorming dielectric, and this stage is followed by the steps below:

[0043] forming a solid electrolytic layer on the dielectric coating;then

[0044] forming a through-hole electrode in the through-holes; and

[0045] forming a collector layer on the solid electrolytic layer.

[0046] A set of steps hitherto discussed is referred to as a stage offorming elements, and this stage is followed by the steps below:

[0047] forming openings at given places of the insulating film on theflat face of the aluminum foil; and

[0048] forming connecting terminals at the openings and on thethrough-hole electrodes.

[0049] A set of steps hitherto discussed is referred to as a stage offorming terminals.

[0050] The present invention allows the solid electrolytic capacitors tobe directly coupled to semiconductor components, and provides amanufacturing method that can manufacture with ease the solidelectrolytic capacitors excellent in high frequency characteristics. Avariety of combinations of steps in a middle stream of themanufacturing-flow will produce various advantages. Some of thoseadvantages are listed below:

[0051] 1. It can prevent solid electrolyte from being formed on the flatface of the aluminum foil, so that an anode and a cathode are positivelyseparated.

[0052] 2. It can prevent the through-hole electrode from extending offthe flat face of the aluminum foil, and also prevent the solidelectrolyte from being formed, so that the anode and the cathode arepositively separated.

[0053] 3. A number of openings can be formed at a time.

[0054] 4. Reliability of the insulation between the through-holeelectrodes and the aluminum foil can be strengthened.

[0055] A use of photosensitive resin or organic adhesive film allowsforming holes at places agreeing with the through-holes by patterning,or positively prevents the resist from entering the through-holes, sothat a solid electrolytic layer is formed on the dielectric coating andin the through-holes. A suitable method of forming resist film can beselected from immersion, spin-coating, screen-printing, or film-bonding,depending on the resist to be used, so that resist film can bepositively formed on the insulating layer.

[0056] Photoresist is applied to both the faces before patterning, andthe through-holes are formed by wet-etching, so that a number ofthrough-holes can be formed at a time through a simple process. Asuitable method of forming through-holes can be selected from laser-beammachining, punching, drilling, or electrical discharge machining,depending on a diameter and the number of the through-holes, so that thethrough-holes can be formed at a lower cost.

[0057] Edges of the through-holes on the porous face of the aluminumfoil can be chamfered off, so that the number of defective insulationcan be reduced.

[0058] A use of electro-deposition method for forming an insulating filmallows forming a thin insulating film with a simple process. Thiselectro-deposition method forms an insulating resin as the first layer,then forms the second layer made from insulating resin produced bymixing micro-gel, carbon fine particles and fine particles of titaniumoxide. In other words, the first layer is thin and has a highresistivity and the second layer can substantially cover edges, so thatthe film is formed with a uniform thickness. As a result, the insulatingfilm on the inner wall of the through-holes has a low defectiveinsulation rate. After conductive adhesive is filled in thethrough-holes for forming the through-hole electrodes, a use of curingmethod can produce capacitors with a simple process and highproductivity.

[0059] After a dielectric coating is formed, a resist film is formed onthe entire face where an insulating film has been formed, then solidelectrolytic layer is formed on the dielectric coating before the resistfilm is removed. This method prevents solid electrolyte from beingformed on the flat face of the aluminum foil, thereby positivelyseparating an anode and a cathode. There is another way to separate theanode from the cathode: After a dielectric coating is formed, a resistfilm is formed on the entire face where an insulating film has beenformed, then a through-hole electrode is formed in the through-holesbefore the resist film is removed. This method prevents the through-holeelectrode from extending off the flat face of the aluminum foil as wellas solid electrolyte from being formed on the flat face, so that theanode and the cathode are positively separated.

[0060] A use of laser-beam machining or grinding with the optimizedoutput can form the openings with ease. Before an insulating film isformed, a resist section is formed on the flat face of the aluminum foilat a given place, then a collector layer is formed before the resistfilm is removed. This method can form a number of openings with ease ata time.

[0061] A use of conductive adhesive in forming a connecting terminalachieves excellent productivity. A use of electro-plating orelectroless-plating can form a number of connecting terminals at a time.

[0062] A use of a composition formed of conductive polymers including aconjugated polymer containing a pi-electron as a material for the solidelectrolytic layer can form a solid electrolytic capacitor having alower ESR and being more thermostable. A use of chemical polimerizationor electrolytic polimerization realizes excellent productivity. Stillother methods are available as follows: Suspension of powder of aconductive polymer is applied and dried, then the conductive polymer isformed by electrolytic polymerization, so that stress applied to thedielectric coating can be reduced. Manganese nitrate is pyrolized (heatdecomposition) to form manganese dioxide, so that solid electrolyticcapacitors can be manufactured positively by an established technique.Manganese nitrate is pyrolized (heat decomposition) to form manganesedioxide, then the conductive polymer is formed by electrolyticpolymerization.

[0063] A collector is formed by a use of suspension of fine particles ofcarbon and by conductive adhesive, so that a solid electrolyticcapacitor having a lower ESR than another solid electrolytic capacitorin which conductive adhesive is directly applied to solid electrolyte.

[0064] The solid electrolytic capacitor of the present invention and amethod of manufacturing the same are demonstrated hereinafter withreference to the accompanying drawings.

[0065] Exemplary Embodiment 1

[0066] The first exemplary embodiment is demonstrated with reference toFIG. 1 through FIG. 14. FIG. 1 shows a perspective view of a solidelectrolytic capacitor in accordance with the first embodiment of thepresent invention. FIG. 2 shows a sectional view of the solidelectrolytic capacitor. FIG. 3 shows an enlarged sectional view of anessential part of the solid electrolytic capacitor.

[0067] First, a structure of sheet-like capacitor element 1 of thepresent invention is described following its manufacturing steps. Etchone of the faces of aluminum foil 2 to form a porous section(hereinafter referred to as porous section 3), then form resist film 4on the porous section. Next, form through-holes 5 in aluminum foil 2 atgiven places, then form insulating films 6 on the non-porous face (flatface) and on the inner walls of the through-holes. Remove resist film 4and form dielectric coating 7 on porous section 3. Then form solidelectrolytic layer 8 on dielectric coating 7 before through-holeelectrodes 9 are formed in through-holes 5. Next, collector layer 10 isformed on solid electrolytic layer 8. Finally, form openings 11 oninsulating film on the flat face at given places, and form connectingterminals 12 at exposed faces of openings 11 and through-hole electrodes9.

[0068] Provide outer case 13 on the lateral faces and collector layer10, and form first external terminal 14 and second external terminal 15,where terminal 14 is electrically coupled to aluminum foil 2 on outercase 13 and terminal 15 is electrically coupled to collector layer 10.Then form connecting bumps 16 both on through-hole electrodes 9 andconnecting terminals 12, so that a solid electrolytic capacitor isbuilt.

[0069] A manufacturing method of the solid electrolytic capacitor of thepresent invention is detailed hereinafter with reference to FIGS. 4-14.As shown in FIG. 4, one of both the faces is etched and the one facebecomes porous. Resist film 4 is formed on porous section 3. A suitablemethod of forming the resist film can be selected from immersion,spin-coating, screen-printing. Photosensitive resin is applied to poroussection 3 by one of the foregoing methods, then the resin is dried,thereby obtaining resist film 4. Organic adhesive film can be used asresist film 4. In this case, resist film 4 is formed on porous section 3by a film bonding method.

[0070] Next, as shown in FIG. 5, through-holes 5 are formed on aluminumfoil 2 at given places. A wet-etching method can form a number ofthrough-holes 5 at a time. Laser-beam machining, punching, drilling orelectric discharge machining is suitable to form through-holes 5 in anymaterials with accuracy, and can form through-holes 5 as fine as notmore than 100 μm across.

[0071] In the case of using the wet-etching, first, form resist filmhaving openings for through-holes on both the faces of aluminum foil 2,then form holes by the wet-etching before the resist film is removed,thereby forming through-holes 5. Further, chamfer the edges ofthrough-holes 5 on porous section 3 of aluminum foils 2 by thewet-etching, so that reliability of insulating film 6 later formed isincreased.

[0072] Next, as shown in FIG. 6, form insulating coat by anelectro-deposition method, so that insulating film 6 can be formed onthe flat face of aluminum foil 2 as well as on the inner walls ofthrough-holes 5. The electro-deposition method can form a fine anduniform film, so that insulating film 6 does not fill up entire hole 5,but covers only the inner wall.

[0073] There is some possibility that insulating film 6 is thinly formedat edges of through-holes 5 on the face where dielectric coating 7 isformed, chamfering the edges is effective to solve this problem and alsoincreases insulation reliability. Further, insulating resin produced bymixing micro-gel, fine-particles of carbon and fine-particles oftitanium oxide, those materials being suitable for covering edges, iselectro-depositioned, thereby solving the problem more effectively.

[0074] The micro-gel discussed above is produced by adding polymericparticles having particle size of not more than 10 μm to a polymer,thereby increasing a viscosity of the polymer. The micro-gel is hard toflow and suitable for covering edges; however, in the case of providingelectro-deposition on the inner wall of through-hole 5 as fine as lessthan 100 μm across, more careful process is required because the mixedresin suitable for covering edges sometimes makes the electro-depositionlayer thick enough for through-hole 5 to be filled up with the mixedresin. Thus the process of forming insulating film 6 byelectro-desposition is split into two steps. First, provide thin resinof high resistivity as a first layer, then provide insulating resinformed by mixing micro-gel, fine particles of carbon and fine particlesof titanium oxide, those materials suitable for covering edges, as asecond layer. As a result, insulating film 6 of fewer insulation defectsis formed on the inner wall of through-holes 5.

[0075] Next, as shown in FIG. 7, after resist film 4 is removed,anodizing in acidic solution allows forming dielectric coating 7 onporous section 3 of aluminum foil 2. Then as shown in FIG. 8, solidelectrolytic layer 8 is formed on dielectric coating 7. This layer 8 isformed by forming a polymer layer using a conjugated polymer containinga pi-electron such as polypyrrole or polythiophene, and/or a compositionincluding conductive polymers other than those discussed above throughchemical or electrolytic polymerization. Solid electrolytic layer 8 canbe formed by electrolytic polymerization or by only chemicalpolymerization after the conductive polymer is pre-coated by chemicalpolymerization. The conductive polymer can be formed by electrolyticpolymerization after the suspension of powder of the conductive polymeris applied and dried, or manganese nitrate is impregnated before thermaldecomposition, thereby forming manganese dioxide, then the conductivepolymer can be formed by electrolytic polymerization. There is anotherestablished technique to form solid electrolytic layer 8: Manganesenitrate is thermally decomposited to form manganese dioxide. This methodcan produce a fine electrolytic layer, and adjust a thickness of thelayer arbitrarily, so that the productivity and reliability can beimproved.

[0076] As shown in FIG. 9, the step of forming through-hole electrode 9in through-hole 5 is described. As a material of electrode 9, conductiveadhesive formed by mixing conductive particles such as Ag paste and Cupaste, is filled into through-hole 5, and then cured.

[0077] As shown in FIG. 10, collector layer 10 is formed on solidelectrolytic layer 8. Collector layer 10 is produced by laminatingcarbon layer and Ag-paste layer with conductive adhesive of which majorcomponents are suspension of carbon fine-particles and Ag-paste. Thisstructure allows drawing electric-charges more efficiently.

[0078] As shown in FIG. 11, openings 11 are formed at given places oninsulating film 6 prepared on the flat face of aluminum foil 2 with YAGlaser or a grinding method. Another method for forming openings 11 is,to form a resist section at first on a given place on the flat face ofaluminum foil 2, then form collector layer 10 before the resist sectionis removed, and finally remove the resist on the given place.

[0079] Next, as shown in FIG. 12, connecting terminal 12 is formed onexposed face in opening 11 of insulating film 6 by using one ofconductive adhesive, electroplating or electroless-plating.

[0080] Then as shown in FIG. 13, outer case 13 made from epoxy resin,good for electrical insulation and resistance to humidity, is formedaround capacitor element 1 for protecting element 1 from externalstress, thereby increasing the reliability. Next, as shown in FIG. 14,first external terminal 14 electrically coupled to aluminum foil 2, andsecond external terminal 15 electrically coupled to collector layer 10are formed on outer case 13, so that capacitor element 1 is completed.

[0081] It is desirable to form connecting bumps 16 on connectingterminals 12 and through-hole electrodes 9 in order to increase theconnecting reliability between the capacitor and semiconductorcomponents or electronic components.

[0082] The method discussed above can readily produce the solidelectrolytic capacitors that can be directly connected to semiconductorcomponents and have a faster response to a high frequency.

[0083] Exemplary Embodiment 2

[0084] The second exemplary embodiment of the present invention isdemonstrated hereinafter with reference to FIG. 15 and FIG. 16

[0085] Etch one of the surfaces of aluminum foil 2 to form a poroussection (hereinafter referred to as porous section 3), then form resistfilm 4 on the porous section. Next, form through-holes 5 in aluminumfoil 2 at given places, then form insulating films 6 on the non-porousface (flat face) and on the inner walls of through-holes 5. Removeresist film 4 and form dielectric coating 7 on porous section 3. Thosesteps are the same as those in the first embodiment.

[0086] Then solid electrolytic layer 8 is formed on dielectric coating7. At this time, when the through-hole is not less than 80 μm across,solid electrolytic layer 8 can be sometimes formed on insulating film 6prepared on the flat face of aluminum foil 2. This problem can beovercome by the following methods: First, as shown in FIG. 15,photosensitive resin is applied on insulating film 6 by one ofimmersion, spin-coater, or screen-printing, then the photosensitiveresin is cured for obtaining second resist film 17. Another way is this:adhesive organic film 6 can be used as second resist film 17. In thiscase, the organic film is formed on insulating film 6 by a film bondingmethod. Then as shown in FIG. 16, form holes on second resist film 17 ingiven dimensions at given places corresponding to through-holes 5 by aphoto-process or a machining method.

[0087] Next, form solid electrolytic layer 8 and through-hole electrode9 by the same methods as the first embodiment, then remove second resistfilm 17, so that solid electrolytic layer 8 is not formed on the flatface of aluminum foil 2. As a result, an anode and a cathode can bepositively separated.

[0088] Then, prepare collector layer 10 on solid electrolytic layer 8 bythe same method as the first embodiment, and form openings 11 at givenplaces on insulating film 6 prepared on the flat face of aluminum foil2. Then form connecting terminals 12 on the exposed faces of opening 11and through-hole electrodes 9.

[0089] As discussed above, the second exemplary embodiment provides amanufacturing method of the solid electrolytic capacitors, and themethod can prevents solid electrolytic layer 8 from reaching to openings11 later formed, so that the anode and the cathode are positivelyseparated.

[0090] Exemplary Embodiment 3

[0091] The third exemplary embodiment of the present invention isdemonstrated hereinafter with reference to FIG. 17 and FIG. 18, whichillustrate major steps of a method of manufacturing the solidelectrolytic capacitors in accordance with the third embodiment.

[0092] Etch one of the surfaces of aluminum foil 2 to form a poroussection (hereinafter referred to as porous section 3), then form resistfilm 4 on the porous section. Next, form through-holes 5 in aluminumfoil 2 at given places, then form insulating films 6 on the non-porousface (flat face) and on the inner walls of the through-holes. Removeresist film 4 and form dielectric coating 7 on porous section 3. Thosesteps are the same as those in the first embodiment.

[0093] Then solid electrolytic layer 8 is formed on dielectric coating7. At this time, when the through-hole is not less than 80 μm across,solid electrolytic layer 8 can be sometimes formed on insulating film 6prepared on the flat face of aluminum foil 2. This problem can beovercome by the following methods: As shown in FIG. 17, through-holeelectrode 9 is formed in through-hole 5. As a material of electrode 9,conductive adhesive formed by mixing conductive particles such as Agpaste and Cu paste is filled into through-hole 5, and then cured. Thenas shown in FIG. 18, solid electrolytic layer 8 is formed on dielectriccoating 7, and collector layer 10 is formed on solid electrolytic layer8. This method prevents solid electrolytic layer 8 from being formed onthe flat face of aluminum foil 2.

[0094] Through-hole electrode 9 is prevented from extending off the flatface of aluminum foil 2 by the following method: After dielectriccoating 7 is formed, second resist film 17 is formed on the entire faceof insulating film 6. Next, through-hole electrode 9 is formed inthrough-hole 5, and solid electrolytic layer 8 is formed on dielectriccoating 7, then collector layer 10 is formed on top of that. Finally,second resist film 17 is removed. This method prevents the solidelectrolyte from being formed on the flat face of aluminum foils 2 aswell as through-hole electrode 9 from extending off the flat face.

[0095] Openings 11 are formed at given places on insulating film 6prepared on aluminum foil 2 by YAG laser. This is the same process asthe first embodiment. Another method to form openings 11 is available:Before insulating film 6 is prepared, a resist section is formed inadvance at a given place on the flat face of aluminum foil 2 usingphoto-curable resin. The resist section is removed after collector layeris formed. Connecting terminals 12 are formed on exposed faces ofopenings 11 and through-hole electrodes 9.

[0096] As discussed above, the third exemplary embodiment provides amanufacturing method of the solid electrolytic capacitors, and themethod can prevents solid electrolyte from infiltrating into openings 11later formed, so that the anode and the cathode are positivelyseparated.

[0097] Exemplary Embodiment 4

[0098] The fourth exemplary embodiment of the present invention isdemonstrated specifically hereinafter with reference to FIG. 19 throughFIG. 22, which illustrate major steps of a method of manufacturing thesolid electrolytic capacitors in accordance with the fourth embodiment.

[0099] Etch one of the surfaces of aluminum foil 2 to form a poroussection (hereinafter referred to as porous section 3), then form resistfilm 4 on porous section 3. Next, form through-holes 5 in aluminum foil2 at given places, then form insulating films 6 on the non-porous face(flat face) and on the inner walls of the through-holes. Remove resistfilm 4 and form dielectric coating 7 on porous section 3. Those stepsare the same as those in the first embodiment.

[0100] Then solid electrolytic layer 8 is formed on dielectric coating7. At this time, when the through-hole is not less than 80 μm across,solid electrolytic layer 8 can be sometimes formed on insulating film 6prepared on the flat face of aluminum foil 2. This problem can beovercome by the following methods: As shown in FIG. 19, insulating film6 is formed such that the flat face of aluminum foil 2 is entirelycovered and first through-hole 5 is completely filled up with film 6. Inorder to fill up through-hole 5 completely, insulating film 6 can beformed by repeating electro-deposition of insulating resin severaltimes, or using screen printing or potting of the insulating resin.Next, as shown in FIG. 20, dielectric coating 7 is formed on poroussection 3, then as shown in FIG. 22, second through-holes 18 are formedin insulating film 6. This structure prevents solid electrolytic layer 8from being formed on the flat face of aluminum foil 2.

[0101] Steps following the processes discussed above are the same as thefirst embodiment. To be specific, after through-hole electrodes 9 areformed in second through-holes 18, collector layer 10 is prepared onsolid electrolytic layer 8, and openings 11 are formed at given placeson insulating film 6 prepared on aluminum foil 2. Then connectingterminals 12 are formed on exposed faces of opening 11 and through-holeelectrodes 9.

[0102] As discussed above, the fourth exemplary embodiment provides amanufacturing method of the solid electrolytic capacitors. The methodcan increase insulation reliability between through-hole electrodes 9and aluminum foil 2, and prevent solid electrolyte from reaching toopenings 11 later formed, so that the anode and the cathode arepositively separated.

[0103] Industrial Applicability

[0104] The manufacturing method disclosed in the present invention canreadily manufacture the solid electrolytic capacitors that can beconnected directly to semiconductor components and have a fasterresponse to a high frequency as well as a large capacitance.

1. A method of manufacturing a solid electrolytic capacitor, the methodincluding: a dielectric forming stage where a dielectric coating isformed on a porous surface of a valve metal sheet undergone a poroustreatment, an element forming stage where a solid electrolytic layer anda collector layer are formed on the dielectric coating, and a terminalforming stage where a connecting terminal to an external electrode isformed, wherein the dielectric forming stage comprising the steps in theorder of: (A1) etching one face of the valve metal sheet for producing aporous section; (A2) forming a first resist film on the face having theporous section; (A3) forming a through-hole on the porous face at agiven place; (A4) forming an insulating film on another face, i.e.,non-porous face of the valve metal sheet and on inner wall of thethrough-hole; and (A5) forming a dielectric coating after the firstresist film is removed, wherein the element forming stage comprising thesteps of: (B1) forming a solid electrolytic layer on the dielectriccoating; (B2) forming a through-hole electrode in the through-hole; and(B3) forming a collector layer on the solid electrolytic layer; whereinthe terminal forming stage comprising the steps of: (C1) forming anopening at a given place on the insulating film formed on the anotherface of the valve metal sheet; and (C2) forming a connecting terminal onexposed faces of the opening and the through-hole electrode.
 2. Themethod of manufacturing the solid electrolytic capacitor of claim 1,wherein the element forming stage comprises the steps in the order of(B1), (B2) and (B3).
 3. The method of manufacturing the solidelectrolytic capacitor of claim 2, wherein the element forming stagefurther comprises the steps of: forming a second resist film on theinsulating film before step (B1); and removing the second resist filmfollowing step (B1).
 4. The method of manufacturing the solidelectrolytic capacitor of claim 1, wherein the element forming stagecomprises the steps in the order of (B2), (B1) and (B3).
 5. The methodof manufacturing the solid electrolytic capacitor of claim 1, whereinthe element forming stage further comprises the steps of: (B4) forming asecond resist film on the insulating film before step (B2), and (B5)removing the second resist film, wherein the element forming stagecomprises the steps in the order of (B4), (B2), (B1), (B3) and (B5). 6.The method of manufacturing the solid electrolytic capacitor of claim 1,wherein the dielectric forming stage includes the step of forming athird resist film on the another face, i.e., non-porous face,simultaneously with step (A2), wherein the element forming stagecomprises the steps in the order of (B1), (B2) and (B3), and wherein theterminal forming stage includes the steps of: removing the third resistfilm; and forming an opening at a given place on the another face, i.e.,non-porous face.
 7. The method of manufacturing the solid electrolyticcapacitor of claim 1, wherein the dielectric forming stage includes thestep of forming a third resist film on the another face, i.e.,non-porous face, simultaneously with step (A2), wherein the elementforming stage comprises the steps in the order of (B2), (B1) and (B3),and wherein the terminal forming stage includes the steps of: removingthe third resist film; and forming an opening at a given place on theanother face, i.e., non-porous face.
 8. The method of manufacturing thesolid electrolytic capacitor of claim 1, wherein the dielectric formingstage includes the step of forming the insulating film such that thenon-porous face of the valve metal sheet is covered and the through-holeis filled up with the insulating film, wherein the element forming stagecomprises the steps in the order of step (B1); the step of forming asecond through-hole in the through-hole filled up with the insulatingfilm; the step of forming the through-hole electrode in the secondthrough-hole; and step (B3).
 9. The method of manufacturing the solidelectrolytic capacitor of claim 1, wherein one of photosensitive resinand adhesive photosensitive film is used as the resist film.
 10. Themethod of manufacturing the solid electrolytic capacitor of claim 1,wherein the resist film is formed by a method selected from the groupconsisting of immersion, spin coating, screen printing, and filmlaminating.
 11. The method of manufacturing the solid electrolyticcapacitor of claim 1, wherein step (A3) includes applying photoresist onboth the faces of the porous valve metal sheet, and wet-etching apatterned opening.
 12. The method of manufacturing the solidelectrolytic capacitor of claim 1, wherein step (A3) is carried out by amethod selected from the group consisting of laser-beam machining,punching, drilling, and electric-discharge machining.
 13. The method ofmanufacturing the solid electrolytic capacitor of claim 1, wherein step(A3) further includes chamfering edges of the through-hole formed on theporous face.
 14. The method of manufacturing the solid electrolyticcapacitor of claim 1, wherein step (A4) uses an electro-depositionmethod to form the insulating flm.
 15. The method of manufacturing thesolid electrolytic capacitor of claim 14, wherein step (A4) includesforming insulating resin as a first layer; and forming insulating resinas a second layer by mixing micro-gel, fine carbon particles and fineparticles of titanium oxide.
 16. The method of manufacturing the solidelectrolytic capacitor of claim 1, wherein step (B2) uses conductiveadhesive to form the electrode.
 17. The method of manufacturing thesolid electrolytic capacitor of claim 1, wherein step (C1) is carriedout by one of laser-beam machining and grinding.
 18. The method ofmanufacturing the solid electrolytic capacitor of claim 1, wherein step(C2) uses conductive adhesive to form the terminal.
 19. The method ofmanufacturing the solid electrolytic capacitor of claim 1, wherein step(C2) is carried out by at least one of electro-plating and electrolessplating.
 20. The method of manufacturing the solid electrolyticcapacitor of claim 1, wherein step (B1) uses a composition including aconductive polymer to form the solid electrolytic layer.
 21. The methodof manufacturing the solid electrolytic capacitor of claim 20, whereinthe conductive polymer is a conjugated polymer containing a pi-electron.22. The method of manufacturing the solid electrolytic capacitor ofclaim 1, wherein step (B1) uses at least one of a chemicalpolymerization method and an electrolytic polymerization method.
 23. Themethod of manufacturing the solid electrolytic capacitor of claim 1,wherein step (B1) includes forming a polymer film using suspension ofpowder of the conductive polymer, and providing electrolyticpolymerization on the polymer film.
 24. The method of manufacturing thesolid electrolytic capacitor of claim 1, wherein step (B1) includesforming the solid electrolytic layer comprising manganese dioxide bythermally decomposing manganese nitrate.
 25. The method of manufacturingthe solid electrolytic capacitor of claim 24, wherein step (B1) includesforming conductive polymer by electrolytic polymerization following theprocess of forming the manganese dioxide.
 26. The method ofmanufacturing the solid electrolytic capacitor of claim 1, wherein step(B3) uses suspension of fine carbon particles, and conductive adhesiveto form the collector layer.